I'm thinking of designing a mission to an asteroid, to Eros, and since NASA has already done a mission to this asteroid, I was wondering if anyone knows of any site, document or whatever helps me. I would also like to know the composition of the soil of Eros.
All the data from the NEAR Shoemaker mission is archived at the Small Body Node of the NASA Planetary Data System. Asteroid surface properties (the regolith) is normally measured using images or spectra in the mid/thermal-infrared to determine the thermal inertia. This can vary considerably depending on whether the surface is made from coarse boulders to very fine regolith as shown in slide 10 of this presentation. Unfortunately the NEAR Shoemaker spacecraft did not carry a mid-IR instrument as spacecraft-sized, reliable and rugged detectors for that spectral range were only developed after that mission flew. Rozitis 2016 discusses the determination of the the surface roughness and discusses the determination of the thermal inertia of Eros using the shape model derived by NEAR Shoemaker and ground-based thermal IR measurements.